WO2008047856A1

WO2008047856A1 - Image projection apparatus

Info

Publication number: WO2008047856A1
Application number: PCT/JP2007/070329
Authority: WO
Inventors: Naoaki Tani
Original assignee: Olympus Corporation
Priority date: 2006-10-20
Filing date: 2007-10-18
Publication date: 2008-04-24
Also published as: JP2008102442A

Abstract

An image projection apparatus has first control mode for variably controlling the level of an LED drive current, and a second control mode for variably controlling the duty ratio of the LED drive current. A feature quantity of a display image is detected from a video signal that corresponds to one or a plurality of frames, and based on the feature quantity, either the first control mode or the second control mode or the both are selected, and in the selected control mode, LED drive control is performed.

Description

Specification

Image projection device

Technical field

[0001] The present invention relates to an image projection apparatus.

Background art

Conventionally, in an image projection apparatus such as a projector, as a method of adjusting the brightness of a projected image, a method of controlling the magnitude of a drive current applied to a light source and a pulsed drive current applied to the light source A method for controlling the duty ratio is known.

Patent Document 1: Japanese Patent Laid-Open No. 2005-70443

Disclosure of the invention

[0003] By the way, when using an LED (light emitting diode) as a light source, if you try to adjust the amount of light by increasing or decreasing the LED drive current, the color of the emitted color will change and the color of the projected image will change! / , There was an inconvenience!

In addition, when adjusting the light intensity by controlling the duty ratio of the drive current applied to the light source, there is a disadvantage that the power consumption cannot be effectively reduced compared to the method of increasing or decreasing the drive current. .

[0004] The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide an image projection apparatus capable of effectively reducing power consumption while suppressing a change in color of a projection image. And

[0005] A first aspect of the present invention modulates illumination light emitted from the light source unit based on a light source unit having a plurality of light sources that generate illumination light of different colors and an input video signal. A light modulation unit, and a control unit that drives and controls each light source of the light source unit, wherein the control unit variably controls the magnitude of the drive current of the light source, and the drive of the light source A second control mode for variably controlling the duty ratio of the current, detecting a feature amount of the display image from the video signal corresponding to one or a plurality of frames, and based on the feature amount! / Select one of the control mode and the second control mode! /, Or either of them, or both, and perform image projection to control drive of the light source in the selected control mode Providing equipment.

[0006] According to such a configuration, the illumination light of different colors emitted from the light source unit is guided to the light modulation unit, and the display image is superimposed by performing light modulation based on the video signal. In this case, each light source of the light source unit is in a control mode corresponding to the feature amount of the video signal, specifically, a first control mode in which the light amount is adjusted by variably controlling the magnitude of the light source drive current, In addition, drive control is performed in one of the second control modes in which the light amount is adjusted by variably controlling the duty ratio of the drive current of the light source, or in a control mode in which both are combined. Therefore, the light quantity of each light source can be adjusted by an appropriate control mode corresponding to the feature amount of the display image.

[0007] In the image projection apparatus, the control unit may detect the feature amount for each color of the illumination light and select a control mode for each color of the illumination light.

According to such a configuration, the feature amount of the display image is detected for each color, and the light source of each color is driven and controlled in the control mode selected according to the feature amount according to the feature amount. Therefore, the amount of light can be adjusted according to an appropriate control mode for each color.

[0009] In the image projection device, the control unit detects luminance as a feature amount of the display image, selects the second control mode when the luminance is equal to or higher than a predetermined value, and the luminance is predetermined. The first control mode may be selected when the value is less than the value of.

[0010] According to such a configuration, when the change in color tone with bright display image brightness is easy to understand, the second control mode in which the magnitude of the drive current is not changed is selected. Power to avoid S In addition, when it is difficult to understand the change in color tone when the brightness of the displayed image is dark, the power consumption can be reduced while allowing a slight color change by selecting the second control mode.

[0011] In the image projection device, the control unit detects the brightness of the image for each color of the illumination light, and when the luminance is equal to or higher than a predetermined value, the control unit detects the light source corresponding to the color. When the drive control is performed in the second control mode and the luminance is less than a predetermined value, the light source corresponding to the color may be drive controlled in the first control mode.

[0012] According to such a configuration, the brightness of the display image is detected for each color, and the light source control mode corresponding to each color is selected depending on whether this brightness is a predetermined value or more. The drive control of the light source can be performed.

[0013] In the image projection apparatus, the control unit may detect a bias of a color component as the feature amount of the image and may select a control mode according to the bias of the color component.

As described above, since the deviation of the color component is detected as the feature amount of the image and the control mode is selected according to the deviation of the color component, the deviation of the color component can be reflected in the drive control of the light source. it can. For example, when displaying an image with a color component bias that causes a significant change in color tone, driving the light sources in the second control mode controls the color tone rather than reducing power consumption. To emphasize. On the other hand, when displaying an image with a color component bias that does not cause a significant change in color tone, each light source is driven and controlled in the first control mode, allowing a slight color tone change. Effectively reduce power consumption.

[0015] In the image projection apparatus, the control unit converts the color of the illumination light having a color change due to increase / decrease in drive current larger than a predetermined value as the color component of the display image to the other illumination light. In the case where the number of colors or more than a predetermined value is included, at least the light source corresponding to the color may be dynamically controlled in the second control mode '.

According to such a configuration, a change in color tone due to increase / decrease in drive current is greater than a predetermined value. When displaying an image that includes more colors of illumination light than other colors or a predetermined value, a small amount is displayed. For light sources corresponding to this color, changes in color tone can be prevented by selecting the second control mode that does not increase or decrease the drive current. In this case, for the light sources corresponding to the other colors, the power consumption can be reduced by selecting the first control mode.

In addition, when displaying an image that includes a color of illumination light whose color tone change due to increase / decrease in drive current is greater than a predetermined value, or other colors or less than a predetermined value, all light sources are set in the first control mode. Drive control may be performed. As a result, the power consumption can be effectively reduced while allowing a slight change in color tone.

In the image projection apparatus, the control unit may detect the number of colors in the image and select a control mode according to the number of colors! /.

In this way, the number of colors is detected as the feature quantity of the image, and the control mode is selected according to the number of colors, so that the number of colors can be reflected in the drive control of the light source. For example, color change When displaying an image with a number of colors that appears prominently, color control is more important than power consumption reduction by driving and controlling each light source in the second control mode. On the other hand, when displaying an image with the number of colors such that the color tone does not change significantly, the power consumption is controlled while driving the light sources in the first control mode while allowing some color change. The power S is used to further reduce the power consumption.

[0019] In the image projection apparatus, the control unit may drive and control all of the light sources in the first control mode when the number of colors in the image is less than a predetermined number! /.

[0020] According to such a configuration, for example, when the number of colors in the display image is smaller than a predetermined number, such as a presentation image, the visual influence due to the color change is small. By adopting the first control mode, the power consumption can be effectively reduced.

[0021] A second aspect of the present invention modulates illumination light emitted from the light source unit based on a light source unit having a plurality of light sources that generate illumination light of different colors and an input video signal. A first control mode for variably controlling the magnitude of the drive current applied to each of the light sources, and a control unit for driving and controlling each of the light sources of the light source unit. A second control mode for variably controlling a duty ratio of a drive current applied to the light source, and a color change due to a change in the magnitude of the drive current is larger than a predetermined value. The light source is driven in the second control mode. There is provided an image projection apparatus that controls and controls the light source whose color change is equal to or less than a predetermined value in the first control mode.

[0022] For a light source corresponding to a color having a large change in color tone due to increase / decrease in drive current, if the first control mode for increasing / decreasing drive current is adopted, the color tone will change. Therefore, the light amount of such a light source is adjusted by controlling the drive in the second control mode. Thereby, the color tone change accompanying increase / decrease in drive current can be suppressed. On the other hand, for a light source corresponding to a color whose color tone change is small due to increase / decrease in drive current, the light amount is adjusted by performing drive control in the first control mode. This makes it possible to reduce power consumption while suppressing color changes.

For example, when an LED is used as the light source, there is a change in color tone due to an increase or decrease in drive current for an LED that emits red illumination light or an LED that emits blue illumination light. Since it is smaller than the fixed value, the light amount is adjusted in the first control mode. For LEDs that emit green illumination light, the color change due to increase or decrease in drive current is greater than that of the other light sources, so the light intensity is adjusted in the second control mode.

In addition, the above-described aspects can be used in combination as much as possible.

[0023] According to the image projection device of the present invention, it is possible to effectively reduce the power consumption while suppressing the change in the color of the projection image.

Brief Description of Drawings

FIG. 1 is a side view showing a schematic configuration of an image projection apparatus according to an embodiment of the present invention.

2 is a block diagram showing a schematic internal configuration of the image processing apparatus shown in FIG.

FIG. 3 is a diagram for explaining the operation of the gain adjustment circuit shown in FIG. 2.

FIG. 4 is a diagram for explaining the operation of the gain adjustment circuit shown in FIG. 2.

FIG. 5 is a diagram for explaining a first control mode.

FIG. 6 is a diagram for explaining a second control mode.

FIG. 7 is a graph showing the drive current / single light quantity characteristics and drive current power consumption characteristics of an LED.

FIG. 8 is a diagram showing a change in color tone when the drive current is increased or decreased.

FIG. 9 is a diagram for explaining light amount control of the image projection apparatus according to an embodiment of the present invention.

FIG. 10 is a diagram in which the color tone of each pixel of a display image formed based on a video signal is plotted in the xy space using the three primary colors of sRGB as a reference, and shows an example of a flower image.

FIG. 11 is a diagram in which the color tone of each pixel of a display image formed based on a video signal is plotted in the xy space with the three primary colors of sRGB as a reference, and shows an example of a sunset image.

FIG. 12 is a diagram in which the color tone of each pixel of a display image formed based on a video signal is plotted in the xy space using the three primary colors of sRGB as a reference, and is a diagram showing an example of a presentation image.

13 is a diagram showing a first modification of the light source unit shown in FIG.

FIG. 14 is a diagram showing a second modification of the light source unit shown in FIG. It is a top view when seen from the emission end side of bright light.

15 is a longitudinal sectional view of the light source unit shown in FIG.

FIG. 16 is a diagram for explaining the rotation state and light transmission efficiency of a rotating rod provided in the light source unit shown in FIG.

FIG. 17 is a diagram showing the magnitude relationship between the maximum current values of the drive currents of the LEDs of the respective colors provided in the light source unit according to the second modification.

FIG. 18 is a diagram showing an example of light amount control of LEDs of respective colors included in a light source unit according to a second modification.

FIG. 19 is a diagram showing an example of light amount control of LEDs of respective colors included in a light source unit according to a second modification.

FIG. 20 is a diagram showing the relationship between the angle of the rotating rod and the light transmission efficiency according to the second modification.

FIG. 21 is a diagram showing a schematic configuration of an image projection apparatus according to a third modification.

Explanation of symbols

1 Image projector

2 Light source unit

2a, 2b, 2c LED

3 Light guide unit

4 transmissive LCD panel

6 Photosynthetic element

10 Control unit

11 Image processing circuit

12 Panel drive circuit

13 CPU

14 Light source drive circuit

18 User I / F

19 Power circuit

S screen BEST MODE FOR CARRYING OUT THE INVENTION

An image projection apparatus according to an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the image projection apparatus 1 according to the present embodiment includes a light source unit 2, a light guide unit 3 that guides illumination light emitted from the light source unit 2, and illumination guided by the light guide unit 3. A transmissive liquid crystal display panel (light modulator) 4 that modulates light and a projection optical unit 5 that projects illumination light modulated by the transmissive liquid crystal display panel 4 onto a screen S are provided. For the sake of simplicity, illustration of the polarizing plate and the like is omitted.

The light source unit 2 includes a plurality of light sources that emit illumination lights of different colors and a light combining element 6 that guides the illumination light emitted from each light source to a common optical path.

In the present embodiment, the light source includes an LED 2a that emits red illumination light, an LED 2b that emits green illumination light, and an LED 2c that emits blue illumination light.

The light guide unit 3 has various optical systems such as a taper rod that appropriately adjusts the parallelism and the like.

[0028] In the image projection apparatus having such a configuration, the LEDs 2a, 2b, and 2c are sequentially turned on in a time-sharing manner, and the illumination light is guided to the common light guide unit 3 by the light combining element 6, and this light guide The unit 3 leads to the transmissive liquid crystal display panel 4. The illumination light on which the display image is superimposed by passing through the transmissive liquid crystal display panel 4 is magnified by the projection optical unit 5 and projected onto the screen S. As a result, the display image is projected on the screen S.

In this case, the transmissive liquid crystal display panel 4 is driven and controlled in synchronization with the lighting timing of the LEDs 2a, 2b, and 2c. Specifically, LED2c emits light based on the red video signal during the period in which LED2a emits light, and LED2c emits based on the green video signal in the period in which LED2b emits light. During the period, the transmissive liquid crystal display panel 4 is driven and controlled based on the blue video signal. Since the light emission periods of the LEDs 2a, 2b, and 2c are set to be very short, the observer can have a visual effect that is almost the same as when white illumination light is irradiated.

The LEDs 2a, 2b, 2c and the transmissive liquid crystal display panel 4 are controlled by the control unit 10. The control unit 10 includes an image processing circuit 11, a panel drive circuit 12, a CPU 13, and a light source drive circuit 14 as main components.

A video signal is input to the image processing circuit 11. The image processing circuit 11 performs known image processing such as interpolation processing and gradation correction processing on the input video signal, and detects the feature amount of the display image based on the video signal corresponding to one frame. .

For example, as shown in FIG. 2, the image processing circuit 11 includes a γ correction circuit 15, a feature amount detection circuit 16, and a gain adjustment circuit 17 as main components. The γ correction circuit 15 generates a linear video signal by performing γ correction on the video signal. The feature amount detection circuit 16 detects the feature amount of the display image based on the video signal corresponding to one frame input from the γ correction circuit 15, outputs the detected feature amount to the CPU 13, and outputs a gain adjustment circuit 17. The feature amount and the video signal are output to

For example, the feature amount detection circuit 16 detects feature amounts relating to the luminance of each color from the video signal corresponding to one frame, specifically, the maximum gradation values Rmax, Gmax, Bmax, and these maximum gradation values Rmax. , Gmax, Bmax are output to the CPU 13, and the maximum gradation values R max, Gmax, Bmax and the video signal are output to the gain adjustment circuit 17.

The gain adjustment circuit 17 adjusts the level of each light quantity of red, green, and blue, outputs the adjusted video signal to the panel drive circuit 12, and outputs the adjustment state to the CPU 13. Specifically, when the maximum gradation values Rmax, Gmax, and Bmax of each color in the display image are input from the feature amount detection circuit 16, the gain adjustment circuit 17 inputs the maximum gradation values Rmax, Gmax, and Bmax into the image. The gradation value of each pixel of the video signal is corrected so that the maximum display gradation value (for example, 255) of the projection apparatus is obtained, and the corrected video signal is output to the panel drive circuit 12. For example, when the maximum display gradation value of the image projector is 255, the gain adjustment circuit 17 applies 255 / Rmax to the gradation value of each pixel of the video signal as shown in FIG. The video signal related to the panel transmittance is corrected, and the corrected video signal is output to the panel drive circuit 12.

The gain adjustment circuit 17 outputs to the CPU 13 a value obtained by correcting the gradation value of the video signal output to the panel drive circuit 12 to be higher. Specifically, as described above, the gradation of each pixel When 255 / Rmax is multiplied by the value, this coefficient 255 / Rmax is output to CPU13.

As shown in FIG. 4, the CPU 13 corrects the light quantity by multiplying the light quantity of each color by the reciprocal Rmax / 255 of this coefficient.

In this way, while increasing the transmittance of the transmissive liquid crystal display panel 4, the amount of light is reduced by the amount corresponding to this increase, so each brightness without changing the brightness of the projected image finally displayed on the screen. It is possible to effectively reduce the light emission amount of the LEDs 2a, 2b, 2c. Thereby, power consumption can be reduced. In the above description, an example is given regarding red, but the same applies to green and blue.

Referring back to FIG. 1, the panel drive circuit 12 changes the transmittance of the transmissive liquid crystal display panel 4 for each pixel based on the gradation value of the video signal from the image processing circuit 11. Thereby, the transmittance of each pixel of the transmissive liquid crystal panel 4 is adjusted according to the video signal. As a result, as described above, the illumination light incident on the transmissive liquid crystal display panel 4 is not converted into the video signal. The display image based on it will be superimposed.

Further, the CPU 13 generates control signals for driving and controlling the respective LEDs 2a, 2b, and 2c based on the feature amount and the video signal from the image processing circuit 11, and the generated control signals are used as the light source driving circuit. Output to 14. Specifically, the CPU 13 variably controls the magnitude of the drive current of each LED 2a, 2b, 2c to adjust the amount of light emitted from each LED 2a, 2b, 2c, and each LED 2a , 2b, 2c by controlling the duty ratio of the drive current, respectively, and a second control mode for adjusting the amount of light emitted from each LED 2a, 2b, 2c.

Then, the CPU 13 selects one or both of the first control mode and the second control mode according to the feature amount, and sends control signals for the LEDs 2a, 2b, 2c based on the selected control mode. These are generated and output to the light source drive circuit 14.

The light source drive circuit 14 applies a drive current to each LED 2a, 2b, 2c based on each control signal from the CPU 13. As a result, the light emission amounts of the LEDs 2a, 2b, 2c are controlled based on the video signal.

Further, the CPU 13 is supplied with a mode instruction signal from the user I / F 18 and a power signal from the power circuit 19. User I / F18 has mode specified by user If it is, a signal corresponding to the designated mode is output to the CPU 13 as a mode instruction signal. The power supply circuit 19 determines whether power is supplied from an AC adapter (not shown) or power is supplied from a notch (not shown). Output to CPU13 as power supply signal.

[0038] Next, the first control mode and the second control mode will be described in detail.

As shown in FIG. 5, the first control mode is a control mode in which the amount of light of each LED 2a, 2b, 2c is adjusted by increasing or decreasing the magnitude of the drive current of each LED 2a, 2b, 2c. In FIG. 5, the maximum current Imax is set to, for example, the maximum value that can be applied to each LED 2a, 2b, 2c during normal operation. This maximum current Imax is a value that can be set individually for each LED 2a, 2b, 2c.

Thus, in the first control mode, the amount of light emitted from each LED 2a, 2b, 2c is adjusted by changing the magnitude of the drive current applied to each LED 2a, 2b, 2c.

[0039] As shown in Fig. 6, the second control mode is a control mode in which the light intensity of each LED 2a, 2b, 2c is adjusted by variably controlling the duty ratio of the drive current of each LED 2a, 2b, 2c. The As shown in FIG. 6, in the second control mode, the magnitude of the drive current applied to each LED 2a, 2b, 2c is not changed, for example, by making the maximum current Imax constant and adjusting the current application time, Adjust the amount of light emitted from each LED2a, 2b, 2c.

Here, FIG. 7 shows general characteristics of the light amount and the power consumption with respect to the drive current of each LED 2a, 2b, 2c.

In FIG. 7, the horizontal axis represents relative drive current, and the vertical axis represents relative light intensity or power consumption.

As shown in FIG. 7, the light quantity of each LED 2a, 2b, 2c tends to saturate when the drive current increases to some extent. In addition, the power consumption of each LED2a, 2b, 2c increases as the drive current increases, and the increase width Δ 電流 gradually increases as the applied current increases (in Fig. 7, Δ において 1 <Δ Ρ2 ). This is because the forward effect voltage of LEDs 2a, 2b, and 2c slightly increases as the drive current increases.

[0041] Because of such characteristics, for example, when reducing the amount of light of the LEDs 2a, 2b, 2c, if the drive current is reduced without changing the duty ratio, the power consumption is reduced. It can be seen that the force can be effectively reduced. For example, in Fig. 7, taking LED2b that emits green illumination light as an example, if the light intensity is reduced from 4 to 2, the drive current will be reduced from about 9 to about 2.7. In addition, the power consumption at this time decreases from about 20 to about 4. For this reason, when the amount of light is reduced by 50%, the drive current can be reduced by about 70% and the power consumption can be reduced by about 83%. On the other hand, even if the duty ratio is reduced to 1/2 in the noise drive, the power consumption is only 50%.

For this reason, the first control mode is compared with the second control mode by the force S, which effectively reduces the power consumption.

Next, FIG. 8 is a diagram showing on the xy color diagram the color expression gamut of red, green, and blue light from the LEDs 2a, 2b, and 2c. When the drive current of each LED2a, 2b, 2c is small, it has a wide color gamut as shown by the broken line in the figure, but when the drive current of each LED2a, 2b, 2c is large, red, green, blue Each color tone changes as indicated by the solid line in the figure, and the color expression range tends to narrow. Also, as shown in this figure, it can be seen that the color tone of the illumination light changes greatly with the increase or decrease of the drive current, especially in the LED 2b that emits green illumination light. On the other hand, for LED 2a that emits red illumination light and LED 2c that emits blue illumination light, the color change due to increase or decrease in drive current is hardly affected by the drive current.

[0043] As shown in FIG. 5, the first control mode that variably controls the magnitude of the drive current of the LEDs 2a, 2b, and 2c is highly effective in reducing the power consumption. As shown in FIG. 8, it has a characteristic that the color tone of the green illumination light changes.

Therefore, in the image projection apparatus according to the present embodiment, focusing on the above points, the following light source control that effectively reduces power consumption while suppressing color change is performed. Yes.

First, when a video signal is input to the image processing circuit 11 of the control unit 10, γ correction is performed on the video signal by the γ correction circuit 15 shown in FIG. 2, followed by the feature amount detection circuit 16. The feature amount detection process is performed. Specifically, the feature quantity detection circuit 16 uses a feature quantity related to the brightness of the display image from the video signal corresponding to one frame, for example, the maximum gradation of each color. Detects max, Gmax, Bmax, outputs these maximum gradation levels Rmax, Gmax, Bmax to the CPU 13, and outputs these maximum gradation levels Rmax, Gmax, Bmax and the video signal to the gain adjustment circuit 17. .

The gain adjustment circuit 17 adjusts the level of the video signal of each color based on the maximum gradation values Rmax, Gmax, and Bmax, thereby generating a video signal related to the panel transmittance and a video signal related to the light amount. The video signal related to the transmittance is output to the panel drive circuit 12 and the video signal related to the light quantity is output to the CPU 13.

[0047] When the maximum gradation values Rmax, Gmax, Bmax and the value for correcting the light intensity are input, the CPU 13 determines whether the maximum gradation values Rmax, Gmax, Bmax are equal to or greater than a preset threshold value. For the LED corresponding to the color for which the maximum gradation values Rmax, Gmax, and Bmax are determined to be greater than or equal to the threshold value, control by the second control mode is selected, and the maximum gradation value is less than the threshold value. The first control mode is selected for the LED corresponding to the color judged to be present.

[0048] For example, when the maximum gradation value Rmax of red is the maximum value (for example, 255),

As indicated by a in 9, the CPU 13 generates a control signal that applies the maximum current Irmax to the LED 2 a for a period of one frame, and outputs this to the light source drive circuit 14.

[0049] If the maximum gradation value Rmax of red is less than the maximum value and greater than or equal to the threshold value,

As shown in b of 9, the CPU 13 generates a control signal having a duty ratio corresponding to the maximum gradation value Rmax for the LED 2 a and outputs the control signal to the light source driving circuit 14. Here, the current application time is set longer as the maximum gradation straight Rmax is larger. It should be noted that an optimal value can be selected for the panelless driving cycle depending on the design items.

[0050] When the maximum red gradation value Rmax is less than the threshold, the CPU 13 has a predetermined duty ratio with respect to the LED 2a as shown in c of FIG. Then, a control signal in the form of a current corresponding to the maximum gradation value Rmax is generated and output to the light source driving circuit 14. Here, the predetermined duty ratio is determined by adopting the duty ratio when the maximum gradation value Rmax matches the threshold value.

Note that the CPU 13 does not increase or decrease the current value in the pulse-like waveform, as shown in FIG. 9c, and the current corresponding to the maximum gray level straight Rmax is 1 frame as shown in FIG. A control signal that is continuously applied over a period may be generated. The CPU 13 similarly generates control signals for the LEDs 2b and 2c and outputs them to the light source drive circuit 14.

When the light source drive circuit 14 receives the control signal generated in this way, the light source drive circuit 14 applies a drive current based on each control signal to each LED 2a, 2b, 2c.

As a result, the LEDs 2a, 2b, and 2c of each color emit light sequentially with the light amount corresponding to the maximum gradation values Rmax, Gmax, and Bmax, and each illumination light is transmitted through the color composition unit 6 and the light guide unit 7 to the transmissive liquid crystal display. After being guided to the display panel 4 and subjected to light modulation based on the video signal, it is projected onto the screen S by the projection optical unit 5. As a result, the projected image is displayed on the screen S.

As described above, according to the image projection apparatus according to the present embodiment, the feature amount related to the luminance of the display image is detected from the video signal corresponding to one frame, and the control mode is set based on the detection result. Since the selection is made, each LED 2a, 2b, 2c can be driven and controlled in an optimal control mode according to the brightness of the display image.

Specifically, when the change in color tone with brighter brightness of the displayed image appears remarkably, the second control mode that does not change the magnitude of the drive current is selected to reduce the color tone rather than reducing the power consumption. Emphasis on.

If it is difficult to see the change in color tone when the brightness of the displayed image is dark, the first control mode is selected to emphasize the reduction of power consumption over the change in color tone.

This makes it possible to adjust the amount of light according to the characteristics of each frame image, and to effectively reduce power consumption while suppressing changes in color tone.

Further, according to the image projection apparatus according to the present embodiment, the brightness of the display image is detected for each color, and each LED 2a, 2b, 2c is driven and controlled in a control mode corresponding to the brightness, so that all the LEDs 2a, 2b , 2c can be driven more precisely than in the case of driving control in the same control mode.

In the present embodiment, it is preferable that the threshold value used by the CPU 13 is set individually for each color. For example, as shown in FIG. 8, for red and blue, the change in color tone due to increase / decrease in the drive current is small, so the power consumption can be effectively reduced by setting the threshold value higher. 1 Actively adopt control mode For green, the change in color tone due to increase / decrease in drive current is larger than that for other colors, so setting the above threshold value lower than for other colors results in a change in color tone and a reduction in power consumption. Adjust the balance. As a result, power S can be reduced more effectively to reduce power consumption.

[0054] In the present embodiment, the force is such that the maximum gradation value is detected from the video signal corresponding to one frame and the control mode can be switched in one frame period.

Further, it may be configured such that the control mode can be switched at a period of a plurality of frames by detecting the maximum gradation value of the video signal power corresponding to the plurality of frames.

In the present embodiment, the maximum gradation value of each color of the display image formed based on the video signal is detected, and the control is adopted depending on whether or not the maximum gradation value is equal to or greater than the threshold value. Force S, which determined the mode, instead of this, the average gradation value in the display image is obtained for each color, and the second control mode (see Fig. 6) is adopted when this average gradation value is equal to or greater than the threshold value. When the average gradation value is less than the threshold value, the first control mode (see Fig. 5) or the control mode that combines the second control mode and the first control mode (see Fig. 9c) is adopted. This is good.

[0056] Further, when determining whether or not the display image is bright, instead of the above method, the display image is detected by detecting pixels for which the gradation value is greater than or equal to the threshold for each color. The second control mode (see Fig. 6) is adopted when the number of pixels is greater than or equal to the preset reference number of pixels, and the first control mode is selected when the number of pixels is less than the reference number of pixels. (Refer to Fig. 5) Alternatively, it may be possible to adopt a control mode (see c in Fig. 9) that is a combination of the second control mode and the first control mode.

[0057] Further, the method for determining whether the display image is bright or not is not limited to the method described above. In short, the second control mode that does not change the color tone is set when the criteria for judging whether or not the display image is bright is set appropriately and the display image is judged to be bright based on this criteria. If it is determined that the displayed image is long, the first control mode is accompanied by a change in color tone but has a high power consumption reduction effect, or a control mode that combines the second control mode and the first control mode. Should be adopted.

In the present embodiment, the maximum luminance value is detected for each color, and based on this maximum luminance value. Therefore, the power to select the control mode of each LED2a, 2b, 2c. Instead, all LEDs 2a, 2b, 2c are the same according to the overall brightness of the display image including red, green, and blue. It ’s a good idea to do this in the wholesale mode!

The ability to determine whether the display image is bright or not can be determined arbitrarily. For example, pixels with a gradation value greater than or equal to a predetermined value are extracted from the video signal in one frame, and the number of pixels is If the number of pixels is equal to or greater than the preset reference pixel number, the display image is judged to be bright and all LEDs 2a, 2b, 2c are driven and controlled in the second control mode. If it is less than the number, it may be determined that the display image is long and all the LEDs 2a, 2b, 2c may be driven and controlled in the first control mode. Further, an average gradation value in one frame may be obtained, and it may be determined whether or not the display image is bright based on whether or not the average gradation value is equal to or greater than a threshold value.

In this embodiment, when the CPU 13 receives a mode designation signal from the user I / F 18, the control mode designated by the user may be preferentially adopted. For example, when the CPU 13 receives a signal for designating the first control mode from the user I / F 18, it drives and controls the LEDs 2a, 2b, 2c in the first control mode. Thus, by adopting the control mode desired by the user with priority, the user's intention can be reflected in the drive control of the LEDs 2a, 2b, 2c.

The user may select a control mode for each color. As a result, the user's intention can be reflected in more detail. In addition to the control mode alone, for example, a judgment criterion for judging whether the display screen is bright or not, such as the threshold value and the number of reference pixels, can be configured by the user! /, .

In the present embodiment, the CPU 13 may switch the control mode based on the power signal from the power circuit 19. For example, since power is supplied from the AC adapter and the power signal indicating the state of V is input, the power that can be consumed is not limited. Employing modes emphasizes color tone over power consumption. On the other hand, during the period when the power supply signal indicating that the power is being supplied from the battery is input, the usable power is limited. Therefore, the CPU 13 operates in the first control mode or the first control described above. Consists of a combination of control mode and second control mode By adopting the control mode, the effect of reducing power consumption is enhanced while allowing color change. Thus, the control mode may be switched according to the power supply state. In addition, when power is supplied from the battery, the control mode can be switched according to the remaining capacity of the battery! /.

In addition, it is possible to apply each aspect mentioned above combining in the possible range.

[Second Embodiment]

Next, an image projection apparatus according to a second embodiment of the present invention will be described. In the image projection apparatus according to the present embodiment, the first control mode is adopted for colors having a small color change due to increase / decrease in drive current, i.e., red and blue, and colors having a large color change due to increase / decrease in drive current, That is, the second control mode is adopted for green. As described above, according to the image projection apparatus of the present embodiment, the control mode is properly used for each color, so that the processing load on the image processing circuit 11 and the CPU 13 can be greatly reduced.

[Third Embodiment]

Next, an image projection apparatus according to a third embodiment of the present invention will be described. The image projection apparatus according to the present embodiment is based on the first embodiment described above in that the control mode is selected according to the color component bias of the display image formed based on the video signal! Different from the image projector.

Hereinafter, the difference between the image projection apparatus according to the present embodiment and the first embodiment will be mainly described.

FIG. 10 and FIG. 11 are diagrams in which the color tone of each pixel of the display image formed based on the video signal is plotted in the xy space with reference to the three primary colors of sRGB. An example of an image is shown in Fig. 11.

In Fig. 10, since the color tone plot of the pixel has a wide S in the triangular color expression range surrounded by the three primary colors of RGB, it can be seen that this display image contains various color components. In contrast, in Fig. 11, the pixel color plot is close to the R primary color in the triangular color expression range surrounded by the three primary colors RGB! Is close to the primary colors of G (green) and B (blue) and contains almost no ingredients! / ,! [0064] The control unit 10 of the image projection apparatus according to the present embodiment detects the color tone deviation of the display image from the video signal corresponding to one frame in the feature amount extraction circuit 16, and the CPU 13 based on the detection result. Determines the control mode to be adopted. Here, the color tone of each pixel can be easily determined by performing a matrix calculation process using a known technique, for example, using the RGB signal level of each pixel in the video signal and the matrix of each tristimulus value XYZ of the RGB primary colors. It can be sought.

When there is no color tone bias, the CPU 13 adopts the second control mode to suppress the color change due to the change in the magnitude of the drive current. Further, the CPU 13 adopts the second control mode for a large number of colors (for example, red in the display image shown in FIG. 11) when the color tone is uneven, thereby increasing the drive current. The color change due to the change in height is suppressed, while for the rarely included colors (for example, green and blue in Fig. 11), the first control mode is used to effectively reduce power consumption. Let

[0065] As described above, according to the image projection apparatus of the present embodiment, the control mode is selected based on the color deviation of the display image formed based on the video signal. It is possible to effectively reduce power consumption while keeping the color tone change within an allowable range.

In the present embodiment, the first control mode is always adopted for red and blue that are not affected by the color due to the magnitude of the current, regardless of the color tone, and the color changes according to the change in the magnitude of the current. Only for green, which is easy to do, the control mode may be selected according to the color tone deviation. As described above, the power consumption of the LEDs 2a and 2c can be further reduced by always adopting the first control mode.

[0066] In the present embodiment, as shown in FIG. 12, when the plots on the color map are arranged in a straight line, it is difficult to notice the change in color, so each LED 2a, 2b, 2c is set to the first. Control may be performed in the control mode. For example, as in a presentation image, there are many pixels represented by the same color! /, And in the case of an image, the color tone of each pixel of the display image formed based on the video signal! / Is the three primary colors of sRGB When plotting in the xy space with reference to, the number of points representing the color tone (number of colors) is higher than the natural image shown in Fig. 10 and Fig. 11, where the plot tends to appear linearly as shown in Fig. 12. Less is. If this is the case, don't mind the color change. The first control mode that can effectively reduce power consumption should be adopted.

[0067] [First modification]

In each of the above embodiments, the light source unit 2 has three LEDs 2a, 2b, and 2c that emit illumination lights of different colors. Instead, as shown in FIG. LED groups 2, 2b ′, 2 in which a plurality of LEDs emitting illumination light are arranged in an array on the same plane may be used. In this case, the light amount control method for each LED is the same as described above.

[Second Modification]

Further, instead of the light source unit 2 according to each of the above embodiments, a light source unit 2 ′ as shown in FIGS. 14 to 16 may be used. Fig. 14 is a plan view of the light source unit 2 'when viewed from the emission end side of the illumination light, Fig. 15 is a longitudinal sectional view of the light source unit 2', and Fig. 16 is a diagram of the rotary head 20 included in the light source unit 2 '. It is a figure for demonstrating a rotation state and the transmission efficiency of light.

As shown in FIGS. 14 and 15, in two light source units, a plurality of LEDs 2a, a plurality of LEDs 2b, and a plurality of LEDs 2c are arranged on the same circumference. At the center of this array, there is provided a rotating rod 20 that can rotate around the center axis of the array.

At the free end of the rotating rod 20, there is an incident end 20a for taking in the illumination light emitted from each LED, and the lighting timing of each LED 2a, 2b, 2c arranged on the same circumference is provided. Synchronously, when the rotating rod 20 is rotated around the center axis of the array, the illumination light emitted from the LEDs 2a, 2b, 2c facing the incident end 20a of the rotating rod 20 is incident on the rotating end 20a. It is taken into 20 and led to the incident end of the fixed rod 23 through the rotating rod 20.

[0069] In such a light source unit 2 mm, each LED 2a, 2b, 2c has a desired color (for example, white) so that the combined light of the illumination light when all the LEDs 2a, 2b, 2c are turned on is turned on. Determine the maximum drive current. For example, as shown in FIG. 17, the maximum drive current Irmax of LED2a, the maximum drive current Igmax of LED2b, and the maximum drive current Ibmax of LED2c are set as follows.

ibmax-Irmax, Igmax

For green, which has a large color change due to increase / decrease in drive current, it is shown in Fig. 18. As shown in the figure, the second control mode is adopted, and for red and blue, where the change in color tone due to increase / decrease in drive current is small, the first control mode is adopted to improve power consumption reduction.

[0070] It should be noted that the green power of the display image and the luminance power to be applied are preset threshold values (for example, the luminance corresponding to the amount of light obtained by the entire LED 2b when one LED 2b is completely turned off). In such a case, as shown in FIG. 19, one LED 2b may be completely turned off, and the other LED 2b may be controlled with a duty ratio corresponding to the luminance.

[0071] When the rotating rod 20 is rotated around the central axis of the LEDs 2a, 2b, 2c in the two light source units, as shown in FIG. 16, when the rotation angle Θ of the rotating rod 20 changes, The coupling state between the exit end 20b of the rotating rod 20 and the entrance end 23a of the fixed rod 23 arranged opposite to the exit end 20b changes, and the light transmission efficiency varies. The exit end 20b of the rotating rod 20 and the entrance end 23a of the fixed rod 23 have the same shape, for example, a square. Here, if the rotation angle of the rotating rod 20 is 0 ° when the four sides are coincident, the light transmission efficiency is as shown in Fig. 20 when the rotation angle is 0 ° and 90 °. It is expressed as a sine wave that takes the maximum value and takes the minimum value at rotation angles of 45 ° and 135 °. In this way, the light transmission efficiency shows a periodic change depending on the rotation angle Θ. Is preferably reduced. Thus, by adjusting the light amount, even when the same brightness is obtained, the power consumption can be efficiently reduced.

[Third Modification]

Further, in each of the above-described embodiments, the illumination light emitted from each LED 2a, 2b, 2c is led to the common transmissive liquid crystal display panel 4 through the common light guide unit 3. As shown in FIG. 21, the light guide units 3a, 3b, 3c and the transmission type night-night display non-linears 4a, 4b, 4c may be provided for the LEDs 2a, 2b, 2c, respectively. In this case, each illumination light transmitted through the transmissive liquid crystal display panels 4a, 4b, 4c is guided to the same optical combining element 8, and is combined here and then guided to the projection optical unit 5. .

As described above, the embodiments of the present invention have been described in detail with reference to the drawings. The present invention is not limited to this embodiment, and includes design changes and the like within the scope not departing from the gist of the present invention.

For example, in each of the above-described embodiments, a reflective liquid crystal display panel or DMD (Digital Micro Mirror) may be employed instead of the transmissive liquid crystal display panel 4.

Claims

The scope of the claims

[1] a light source unit having a plurality of light sources that generate illumination lights of different colors;

A light modulation unit that modulates illumination light emitted from the light source unit based on an input video signal;

A control unit that drives and controls each of the light sources of the light source unit;

With

The control unit is

A first control mode for variably controlling the magnitude of the drive current of the light source;

A second control mode for variably controlling the duty ratio of the drive current of the light source;

And detecting a feature amount of a display image from the video signal corresponding to one or a plurality of frames, and based on the feature amount! /, And in the first and second control modes! /, An image projection apparatus that selects one or both and performs drive control of the light source in the selected control mode.

2. The image projection apparatus according to claim 1, wherein the control unit detects the feature amount for each color of the illumination light and selects a control mode for each color of the illumination light.

[3] The control unit detects luminance as a feature amount of the display image, selects the second control mode when the luminance is equal to or higher than a predetermined value, and the luminance is lower than the predetermined value. The image projector according to claim 1, wherein the first control mode is selected.

[4] The control unit detects the luminance of the image for each color of the illumination light, and drives the light source corresponding to the color in the second control mode when the luminance is a predetermined value or more. 4. The image projecting device according to claim 3, wherein when the luminance is less than a predetermined value, the light source corresponding to the color is driven and controlled in the first control mode.

5. The image projecting device according to claim 1, wherein the control unit detects a bias of a color component as a feature amount of the display image and selects a control mode according to the bias of the color component.

[6] The control unit includes, as a color component of the display image, a color of illumination light whose color tone change due to increase or decrease in drive current is larger than a predetermined value, more than the color of other illumination light or a predetermined value 6. The image projection device according to claim 5, wherein at least the light source corresponding to the color is driven and controlled in the second control mode.

7. The image projection apparatus according to claim 1, wherein the control unit detects the number of colors in the display image and selects a control mode according to the number of colors.

8. The image projection apparatus according to claim 7, wherein the control unit drives and controls all the light sources in the first control mode when the number of colors in the display image is less than a predetermined number! /.

[9] a light source unit having a plurality of light sources that generate illumination lights of different colors;

With

The control unit is

A first control mode for variably controlling the magnitude of the drive current applied to each light source; and a second control mode for variably controlling the duty ratio of the drive current applied to each light source. The light source whose color change due to the change in color is greater than a predetermined value is driven and controlled in the second control mode, and the light source whose color change is less than or equal to the predetermined value is driven and controlled in the first control mode. Image projection device.